There are many ways to generate steam for humidification purposes. For example, electrode-type humidifiers produce a small to moderate amount of steam at low pressure (usually atmospheric). In this type of system, electrodes are placed in a plastic tank and electricity is applied to the electrodes directly located in water. As typical water conducts electricity, the water is heated and caused it to boil as the electricity travels through the water between the electrodes. Electrode humidifiers have inherent steam output control limitations. Operation is dependent upon and varies with the water conductivity. Steam output is controlled by draining and filling with water, which adjusts water conductivity and water level. Very low conductivity water such as RO (reverses osmosis) and DI (deionized) renders an electrode humidifier virtually inoperable
Electrode humidifiers also require that any connected drain lines either be physically separated from the electrically charged water or that the electrodes be turned off the prevent shock hazards during draining. However, electrode humidifiers are typically lower cost than other steam humidifiers, fail safe under low/no water conditions and have replaceable tanks with electrodes for easier maintenance.